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A caster (or castor) is an undriven, single, double, or compound wheel that is designed to be mounted to the bottom of a larger object (the 'vehicle') so as to enable that object to be easily moved. They are available in various sizes, and are commonly made of rubber, plastic, nylon, aluminum, or stainless steel.

These caster wheels are normally connected in the front side of the robotic car in the center for balance, while motors and wheels are connected on the back side of the robotic car.